Light-emitting diode chip

ABSTRACT

A light-emitting diode (LED) chip is disclosed. The chip includes a light-emitting diode and an electrode layer on the light-emitting diode. The electrode layer includes a reflective metal layer. The reflective metal layer includes a first composition and a second composition. The first composition includes aluminum or silver, and the second composition includes copper, silicon, tin, platinum, gold, palladium or a combination thereof. The weight percentage of the second composition is greater than 0% and less than 20%.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.14/325,215 filed on Jul. 7, 2014 and entitled “LIGHT-EMITTING DIODECHIP”, which claims the priority of Taiwan Patent Application No.103107843 filed on Mar. 7, 2014, and the entirety of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light-emitting device, and moreparticularly to a light-emitting diode chip including a reflective metallayer.

2. Description of the Related Art

Various light-emitting devices have advanced with development andadvances in technology to satisfy consumers in the modern world. Amongthe various light-emitting devices, there has been a trend forlight-emitting diodes (LEDs) to gradually replace traditionalilluminated devices (for example, fluorescent lamps and incandescentlights) due to advantages such as low heat generation, low powerconsumption, their long lifespan, and small size.

Generally, an LED chip includes an LED and an electrode layerelectrically coupled to the LED. The electrode layer may include areflective metal layer, which reflects light emitted from the LED to theoutside environment, such that the light efficiency of the LED chip canbe further improved.

Aluminum or silver is a common material for the reflective metal layersince it is highly reflective of visible light. Aluminum or silver,however, are prone to deterioration due to occurrence ofelectro-migration under high-current operation, which adversely impactsthe light efficiency and the reliability of the LED chip.

Therefore, there is a need for a novel reflective metal layer that iscapable of mitigating electro-migration therein while maintaining thereflectivity thereof, thereby improving the overdrive performance of theLED chip.

BRIEF SUMMARY OF THE INVENTION

A detailed description is given in the following embodiments withreference to the accompanying drawings. A light-emitting diode chip isprovided.

An exemplary embodiment of light-emitting diode (LED) chip comprises anLED and an electrode layer on the LED. The electrode layer comprises areflective metal layer. The reflective metal layer comprises a firstcomposition and a second composition, wherein the first compositioncomprises aluminum (Al) or silver (Ag), and the second compositioncomprises copper (Cu), silicon (Si), tin (Sn), platinum (Pt), gold (Au),palladium (Pd) or a combination thereof. The weight percentage of thesecond composition is greater than 0% and less than 20%.

An exemplary embodiment of LED chip comprises an LED and an electrodelayer disposed on the LED. The electrode layer comprises a reflectivemetal layer and an adhesive layer that is between the LED and thereflective metal layer. The reflective metal layer comprises a firstcomposition and a second composition, wherein the first compositioncomprises Al or Ag and the second composition comprises Cu, Si, Sn, Pt,Au, Pd or a combination thereof. The weight percentage of the secondcomposition is greater than 0% and less than 20%.

An exemplary embodiment of LED chip comprises an LED and a reflectivemetal layer disposed on the LED. The reflective metal layer comprises afirst composition and a second composition, wherein the firstcomposition comprises Al or Ag and the second composition comprises Cu,Si, Sn, Pt, Au, Pd or a combination thereof. The weight percentage ofthe second composition is greater than 0% and less than 20%.

According to the embodiments of the invention, the grain size of thereflective metal layer can be reduced by adding a few secondcompositions therein, thereby increasing the reflectivity of thereflective metal layer and improving the light efficiency of the LEDchip. Besides, it can be observed from the results of the high currentaging test that electro-migration in the reflective metal layer occursless, thus the overdrive performance of the LED chip can be improved.Furthermore, it is noted that the variation of the operating voltage ofthe LED chip with time is decreased, according to the embodiments of theinvention. Namely, the reliability of the LED chip can be maintainedduring long-term operation, according to the embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thesubsequent detailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a cross-sectional view of an LED chip according to anembodiment of the invention.

FIG. 2 is a cross-sectional view of an LED chip according to anotherembodiment of the invention.

FIG. 3 is a cross-sectional view of an electrode layer according to someembodiments of the invention.

FIG. 4 is an Al—Cu alloy phase diagram.

FIG. 5 is a graph illustrating a comparison of the reflectivity of thereflective metal layer at various wavelengths with respect to differentCu content in the reflective metal layer, according to some embodimentsof the invention.

FIG. 6 is a graph illustrating a comparison of the resistivity of thereflective metal layer with respect to different Cu content in thereflective metal layer, according to some embodiments of the invention.

FIG. 7 is a graph illustrating a comparison of the variation of theoperating voltage of the LED chip with time with respect to different Cucontent in the reflective metal layer, according to some embodiments ofthe invention.

FIG. 8 is a cross-sectional view of a flip-chip LED chip according to anembodiment of the invention.

FIG. 9 is a cross-sectional view of a flip-chip LED chip according to anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode ofimplementing the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

Please refer to FIG. 1, which illustrates a cross-sectional view of anLED chip 10 according to an embodiment of the invention. The LED chip 10includes a substrate 100, an LED 1000 composed of a firstconductivity-type semiconductor layer 101, an active layer 102 and asecond conductivity-type semiconductor layer 103, an ohmic contact layer107 and electrode layers 104 and 105 electrically coupled to the firstconductivity-type semiconductor layer 101 and the ohmic contact layer107, respectively. In the embodiment, the LED chip 10 is ahorizontal-type structure, in which the electrode layers 104 and 105 areprovided on the same side of the LED chip 10.

In the embodiment, the substrate 100 comprises sapphire, SiC, Si or anyknown LED substrates, which may act as a growth substrate for formingthe LED 1000.

In the embodiment, the first conductivity-type semiconductor layer 101and the second conductivity-type semiconductor layer 103 comprise aIII-V type semiconductor, such as GaN, AlGaN, InGaN, AlInGaN, GaP,GaAsP, GaInP, AlGaInP, AlGaAs or a combination thereof. The firstconductivity-type semiconductor layer 101 and the secondconductivity-type semiconductor layer 103 may be formed by any suitablemethods, such as chemical vapor deposition (CVD), metal organic chemicalvapor deposition (MOCVD), plasma enhanced chemical vapor deposition(PECVD), molecular beam epitaxy, hydride vapor phase epitaxy orsputtering. In an embodiment, the first conductivity-type semiconductorlayer 101 is a N-type semiconductor layer and the secondconductivity-type semiconductor layer 103 is a P-type semiconductorlayer. In another embodiment, the first conductivity-type semiconductorlayer 101 is a P-type semiconductor layer and the secondconductivity-type semiconductor layer 103 is a N-type semiconductorlayer.

In the embodiment, the active layer 102 comprises a multiple quantumwell (MQW) structure composed of a stack of barrier layers and quantumwell layers (not shown) in an alternating arrangement. For example, theactive layer 102 may comprise a stack of alternating GaN/InGaN, in whichGaN acts as a material for the barrier layer and InGaN act as a materialfor the quantum well layer, but it is not limited thereto. The activelayer 102 may be formed by methods similar to those for forming thefirst conductivity-type semiconductor layer 101 and the secondconductivity-type semiconductor layer 103, and are not described againin detail herein.

In the embodiment, the ohmic contact layer 107 may comprise indium tinoxide (ITO) or any suitable conducting materials, which may be formed bysputtering, evaporation or any suitable methods. The ohmic contact layer107 is capable of reducing the energy barrier between the electrodelayer 105 and the second conductivity-type semiconductor layer 103, suchthat the electrode layer 105 is in ohmic contact with the secondconductivity-type semiconductor layer 103.

Please refer to FIG. 2, which illustrates a cross sectional view of anLED chip 20 according to another embodiment of the invention, whereinelements in FIG. 2 that are the same as those in FIG. 1 bear the samereference numbers. The LED chip 20 comprises an LED 1000 composed of afirst conductivity-type semiconductor layer 101, an active layer 102 anda second conductivity-type semiconductor layer 103, and electrode layers104 and 105 electrically coupled to the first conductivity-typesemiconductor layer 101 and the second conductivity-type semiconductorlayer 103, respectively. In the embodiment, the LED chip 20 is avertical-type structure. The difference between the embodiment of FIG. 2and that of FIG. 1 lies in that the electrode layers 104 and 105 of FIG.2 being respectively disposed on the upper and lower sides of the LEDchip 20 rather than on the same side.

Please referring to FIG. 3, which illustrates a cross sectional view ofan electrode layer 104 according to some embodiments of the invention.It is appreciated that the electrode layer structure described below mayapply to the electrode layer 105 or electrode layers for other types ofthe LED chips. In the embodiment, the electrode layer 104 comprises afirst adhesive layer 200, a reflective metal layer 201, a secondadhesive layer 202, a diffusion barrier layer 203 and a bonding layer204 stacked sequentially.

In the embodiment, the first adhesive layer 200 comprises Cr, Ti, Pd,Pt, Ni, Au, Ag or a combination thereof, which may reduce the energybarrier between the electrode layer 104 and the first conductivity-typesemiconductor layer 101, such that the electrode layer 104 is in ohmiccontact with the first conductivity-type semiconductor layer 101.

In the embodiment, the reflective metal layer 201 comprises a firstcomposition. The first composition comprises the metal with highreflectivity with respect to the light having a specific wavelength(e.g., visible light), such that the light emitted to the electrodelayer 104 can be reflected toward the outside environment and thereforethe light efficiency of the LED chip can be improved. In an embodiment,the first composition comprises Al or Ag.

In the embodiment, the reflective metal layer 201 further comprises asecond composition comprising Cu, Si, Sn, Pt, Au, Pd or a combinationthereof. According to the experimental results described below, theelectro-migration in the reflective metal layer 201 is mitigated byadding the second composition therein. Furthermore, as compared with thereflective metal layer 201 without adding the second composition (e.g.,pure aluminum or pure silver), the reflective metal layer 201 with thesecond composition added has a relatively smaller grain size, such thatthe reflectivity thereof can be increased.

In an embodiment, the percentage of the second composition in thereflective metal layer 201 is less than 20% to prevent the reflectivityof the reflective metal layer 201 from decreasing due to the proportionof the first composition in the reflective metal layer 201 becoming toolow.

In an embodiment, the first composition of the reflective metal layer201 comprises Al, and the second composition of the reflective metallayer 201 comprises Cu. In this embodiment, the reflective metal layer201 may comprise an Al—Cu or Al—Si—Cu alloy. In another embodiment, thefirst composition of the reflective metal layer 201 comprises Ag, andthe second composition of the reflective metal layer 201 comprises Cu.In this embodiment, the reflective metal layer 201 may comprise an Ag—Cuor Ag—Si—Cu alloy. In the subsequent description, the Al—Cu alloy isselected as an example to describe the embodiment of the disclosure. Itis appreciated, however, that the present invention is not limitedthereto.

In an embodiment, the weight percentage (wt %) of Cu of the secondcomposition is in a range of about 0.1%-2%. For example, the weightpercentage of Cu of the second composition may be 1.5%. With respect tothe Al—Cu phase diagram shown in FIG. 4, in the case where thereflective metal layer 201 is an Al—Cu alloy, the above-mentioned rangeof the weight percentage of Cu allows Cu to be stabilized in the α-phasealloy, in which Al is the major composition, under a temperature lowerthan 700° C.

Referring to FIG. 5, which illustrates a comparison of the reflectivityof the reflective metal layer 201 at various wavelengths with respect todifferent Cu content in the reflective metal layer 201, according tosome embodiments of the invention. As shown in FIG. 5, the Al—Cu alloywith 0.5% or 1.5% Cu content has a higher reflectivity to visible lightcompared to pure aluminum without adding Cu therein. For example, forthe wavelength of light ranged between 440 nm-460 nm, the reflectivityof the pure aluminum is 88%, while the reflectivity of the Al—Cu alloywith 0.5% or 1.5% Cu content can be increased to 91%.

In the embodiments mentioned above, the increase of the reflectivity ofthe reflective metal layer 201 results from the reduction of the grainsize. For pure aluminum, the root mean square (RMS) grain size is about12 nm. However, when 0.5% or 1.5% Cu is added into aluminum, the RMSgrain size can be reduced to 0.8 nm. Therefore, the reflectivity of thereflective metal layer 201 can be increased.

Referring to FIG. 6, which illustrates a comparison of the resistivityof the reflective metal layer 201 with respect to different Cu contentin the reflective metal layer 201, according to some embodiments of theinvention. As shown in FIG. 6, there is only a slight increase in theresistivity of the Al—Cu alloy with 0.5% or 1.5% Cu content compared topure aluminum without adding Cu therein (i.e., 0% Cu). Such a slightincrease will not adversely affect the operation of the LED chip.

Referring to FIG. 7, which illustrates a comparison of the variation ofthe operating voltage of the LED chip with time with respect todifferent Cu content in the reflective metal layer, according to theresults of high current aging test. As shown in FIG. 7, as compared tothe embodiment of the pure aluminum, the variation of the operatingvoltage of the LED chip with time becomes lower when Cu is added intothe reflective metal layers 201. Moreover, as Cu content in thereflective metal layer 201 is increased, the variation of the operatingvoltage of the LED chip with time is suppressed as well.

As observed by the electron microscopy in the high current aging test,the crystal structure of the reflective metal layer 201 with Cu addedtherein is less damaged compared to that of the reflective metal layer201 without adding Cu therein (e.g., pure aluminum). Namely, thereflective metal layer 201 with Cu added has better electro-migrationresistance.

Please refer to FIG. 3. In the embodiment, the diffusion barrier layer203 comprises Pt, Ti, W, Ni, Pd or a combination thereof, which canprevent compositions in the bonding layer 204 from diffusing tounderlying layers (e.g., reflective metal layer 201). In an embodiment,the second adhesive layer 202 comprising Cr, Ti, Ni or any suitableadhesive material may be disposed between the diffusion barrier layer203 and the reflective metal layer 201, such that the diffusion barrierlayer 203 is readily bonded to the reflective metal layer 201.

In the embodiment, the bonding layer 204 comprises Au, Sn, Zn, In, Ag ora combination thereof, which is used for bonding and electricallyconnecting the LED to the external components (e.g., wire, conductivebump or solder).

Please refer to FIG. 8, which illustrates a cross-sectional view of aflip-chip LED chip 30 according to an embodiment of the invention. Inthe embodiment, the flip-chip LED chip 30 is also a horizontal-typestructure, in which the electrode layers are provided on the same sideof the flip-chip LED chip 30.

The flip-chip LED chip 30 comprises an LED 3000 composed of a firstconductivity-type semiconductor layer 301, an active layer 302 and asecond conductivity-type semiconductor layer 303 disposed on a substrate300. The substrate 300 may comprise a material that is the same as orsimilar to the material of the substrate 100 shown in FIG. 1.

In the embodiment, the first conductivity-type semiconductor layer 301and the second conductivity-type semiconductor layer 303 of theflip-chip LED 3000 may comprise materials that are the same as orsimilar to the materials of the first conductivity-type semiconductorlayer 101 and the second conductivity-type semiconductor layer 103 ofthe LED 1000, respectively, shown in FIG. 1. Also, the firstconductivity-type semiconductor layer 301 and the secondconductivity-type semiconductor layer 303 of the flip-chip LED 3000 maybe formed by any suitable method, such as CVD, MOCVD, PECVD, molecularbeam epitaxy, hydride vapor phase epitaxy, or sputtering. In anembodiment, the first conductivity-type semiconductor layer 301 is anN-type semiconductor layer and the second conductivity-typesemiconductor layer 303 is a P-type semiconductor layer. In anotherembodiment, the first conductivity-type semiconductor layer 301 is aP-type semiconductor layer and the second conductivity-typesemiconductor layer 303 is an N-type semiconductor layer.

In the embodiment, the active layer 302 of the flip-chip LED 3000 maycomprise a structure that is the same as or similar to that of theactive layer 102 of the LED 1000 shown in FIG. 1, but it is not limitedthereto. Moreover, the active layer 302 may be formed by methods thatare similar to those used for forming the first conductivity-typesemiconductor layer 301 and the second conductivity-type semiconductorlayer 303.

In the embodiment, the flip-chip LED chip 30 further comprises areflective metal layer (including reflective metal layers 401 a and 401b) that is disposed on the second conductivity-type semiconductor layer303 of the LED 3000. The reflective layers 401 a and 401 b are separatedfrom each other by a recess 304 that extends from a top surface of thesecond conductivity-type semiconductor layer 303 into a portion of thefirst conductivity-type semiconductor layer 301. As a result, a portionof first conductivity-type semiconductor layer 301 is exposed from therecess 304. In an embodiment, the reflective metal layers 401 a and 401b may comprise a single layer or a multi-layer structure. In someembodiments, the reflective metal layers 401 a and 401 b may be formedonto the second conductivity-type semiconductor layer 303 of the LED3000 by adhesive layers (not shown) or ohmic contact layers (not shown).In the embodiment, the materials of the reflective metal layers 401 aand 401 b may be the same as or similar to the material of thereflective metal layer 201 shown in FIG. 3. Moreover, the materials ofthe adhesive layers may be the same as or similar to the material of thefirst adhesive layer 200 shown in FIG. 3 and the materials of the ohmiccontact layers may be the same as or similar to the material of theohmic contact layer 107 shown in FIG. 1.

In the embodiment, the flip-chip LED chip 30 further comprises adiffusion barrier layer (including diffusion barrier layers 403 a and403 b) that is disposed on the reflective metal layers 401 a and 401 b.For example, the diffusion barrier layer 403 a is disposed on thereflective metal layer 401 a and the diffusion barrier layer 403 b isdisposed on the reflective metal layer 401 b. In an embodiment, thediffusion barrier layers 403 a and 403 b may comprise a single layer ora multi-layer structure. In some embodiments, the diffusion barrierlayers 403 a and 403 b may comprise the first and second compositions ofthe reflective metal layer 201 shown in FIG. 3. In this case, the weightpercentage of the second composition in the diffusion barrier layers 403a and 403 b is greater than 0% and less than 20%. In an embodiment, theweight percentage (wt %) of Cu of the second composition is in a rangeof about 0.1%-2%. For example, the weight percentage of Cu of the secondcomposition may be 1.5%.

In the embodiment, the flip-chip LED chip 30 further comprises a firstisolation layer 309 that is disposed on the diffusion barrier layers 403a and 403 b and is further extended to cover the reflective metal layers401 a and 401 b, the sidewalls of the recess 304 and the LED 3000.Moreover, the first isolation layer 309 has an opening 309 a to expose aportion of the diffusion barrier layers 403 a. The first isolation layer309 may comprise a dielectric material or any suitable material used fora passivation layer. In some embodiments, a protective layer (not shown)may be disposed on the sidewall of the recess 304 and covered by thefirst isolation layer 309 in the recess 304.

In the embodiment, the flip-chip LED chip 30 further comprises aconductive metal layer 405 that is disposed on the first isolation layer309 above the diffusion barrier layers 403 a and 403 b. Moreover, aportion of the conductive metal layer 405 further extends to fill in therecess 304 and be separated from the sidewalls of the recess 304 by thefirst isolation layer 309, so as to be in contact with the firstconductivity-type semiconductor layer 301. Moreover, the conductivemetal layer 405 has an opening 405 a above the opening 309 a to expose aportion of the first isolation layer 309 and the portion of thediffusion barrier layer 403 a that is exposed from the opening 309 a. Inan embodiment, the conductive metal layer 405 may comprise a singlelayer or a multi-layer structure. In some embodiments, the conductivemetal layer 405 may comprise the first and second compositions of thereflective metal layer 201 shown in FIG. 3. In this case, the weightpercentage of the second composition in the conductive metal layer 405is greater than 0% and less than 20%. In an embodiment, the weightpercentage (wt %) of Cu of the second composition is in a range of about0.1%-2%. For example, the weight percentage of Cu of the secondcomposition may be 1.5%.

In the embodiment, the flip-chip LED chip 30 further comprises a secondisolation layer 311 that is disposed on the conductive metal layer 405and is further extended in the openings 309 a and 405 a to cover thesidewalls thereof. Moreover, the second isolation layer 311 has openings312 a and 312 b corresponding to the diffusion barrier layers 403 a and403 b, respectively. The opening 312 a exposes a portion of thediffusion barrier layers 403 a that is exposed from the opening 309 a.The opening 312 b exposes a portion of the conductive metal layer 405above the diffusion barrier layer 403 b. The second isolation layer 311may comprise a dielectric material or any suitable materials used for apassivation layer. Moreover, the second isolation layer 311 may comprisea material that is the same as or similar to the material of the firstisolation layer 309.

In the embodiment, the flip-chip LED chip 30 further comprises bondinglayers 407 a and 407 b that are individually disposed on the secondisolation layer 311 above the diffusion barrier layers 403 a and 403 b.Namely, the bonding layer 407 a is disposed directly above the diffusionbarrier layer 403 a and the bonding layer 407 b is disposed directlyabove the diffusion barrier layer 403 b. The bonding layers 407 a and407 b serve as bond pads or portions of electrodes for the flip-chip LEDchip 30.

A portion of the bonding layer 407 a passes through the second isolationlayer 311 via the openings 312 a, so as to be in contact with theexposed portion of the diffusion barrier layer 403 a. A portion of thebonding layer 407 b extends through the second isolation layer 311 viathe opening 312 b, so as to be in contact with the exposed portion ofthe conductive metal layer 405.

In an embodiment, the bonding layers 407 a and 407 b may comprise asingle layer or a multi-layer structure. In some embodiments, at leastone of the bonding layers 407 a and 407 b may comprises the first andsecond compositions of the reflective metal layer 201 shown in FIG. 3.In this case, the weight percentage of the second composition in one ofthe bonding layers 407 a and 407 b is greater than 0% and less than 20%.

In the embodiment, the reflective metal layer 401 a, the diffusionbarrier layer 403 a, and the bonding layer 407 a constitute a firstelectrical connecting path that is electrically coupled to the secondconductivity-type semiconductor layer 303 of the LED 3000. Moreover, theconductive metal layer 405 and the bonding layer 407 b constitute asecond electrical connecting path that is electrically coupled to thefirst conductivity-type semiconductor layer 301 of the LED 3000.

In the embodiment, the first and second electrical connecting pathscomprise the first composition, such as Al or Ag, with high reflectivitywith respect to the light having a specific wavelength (e.g., visiblelight). As a result, the light emitted to the first and secondelectrical connecting path can be reflected toward the outsideenvironment and therefore the light efficiency of the flip-chip LED chip30 can be improved.

Moreover, the first and second electrical connecting paths furthercomprises a second composition, such as Cu, Si, Sn, Pt, Au, Pd or acombination thereof. It should be understood that the impact of theelectro-migration is increased under high-current operation. Whenvacancies are formed in the Al-containing current path by the migrationof Al atoms due to the electro-migration effect, these vacancies can befilled by Cu atoms. Accordingly, the electro-migration effect in theelectrical connecting path can be effectively mitigated by the secondcomposition therein. As a result, the reliability of the electricalconnecting path can be improved even under high-current operation.

Additionally, the aluminum-containing electrical connecting path cancorrode easily by the halogen elements from environment. Also, thesecond composition, such as Cu, in the first and second electricalconnecting paths can enhance the resistance to the impurity.Accordingly, the stability of the first and second electrical connectingpaths is also increased.

Please refer to FIG. 9, which illustrates a cross-sectional view of aflip-chip LED chip 30′ according to an embodiment of the invention.Descriptions of elements of the embodiments hereinafter that are thesame as or similar to those previously described with reference to FIG.8 may be omitted for brevity. In the embodiment, the flip-chip LED chip30′ is similar to the flip-chip LED chip 30 shown in FIG. 8. In theembodiment, the flip-chip LED chip 30′ further includes conductive metallayer 405′ that is electrically isolated from the conductive metal layer405 and disposed on the first isolation layer 309 above the diffusionbarrier layer 403 a. Moreover, the conductive metal layer 405′ furtherextends to fill in the opening 309 a, so as to be in contact with theportion of the diffusion barrier layer 403 a that is exposed from theopening 309 a. In an embodiment, the conductive metal layer 405′ maycomprise a single layer or a multi-layer structure. In some embodiments,the conductive metal layer 405′ may comprise the same material as thatof the conductive layer 405.

In the embodiment, the second isolation layer 311 that is disposed onthe conductive metal layers 405 and 405′ and is further extended in theopening 405 a to cover a portion of the sidewall of the conductive metallayers 405′. Moreover, the opening 312 a of the second isolation layer311 exposes a portion of the conductive metal layers 405′.

In the embodiment, a portion of the bonding layer 407 a passes throughthe second isolation layer 311 via the openings 312 a, so as to be incontact with the exposed portion of the conductive metal layers 405′.

In the embodiment, the reflective metal layer 401 a, the diffusionbarrier layer 403 a, the conductive metal layers 405′, and the bondinglayer 407 a constitute a first electrical connecting path that iselectrically coupled to the second conductivity-type semiconductor layer303 of the LED 3000. Moreover, the conductive metal layer 405 and thebonding layer 407 b constitute a second electrical connecting path thatis electrically coupled to the first conductivity-type semiconductorlayer 301 of the LED 3000.

According to the embodiments of the invention, the grain size of thereflective metal layer, the diffusion barrier layer, the conductivelayer, or the bonding layer can be reduced by adding a few secondcompositions therein, thereby increasing the reflectivity thereof andimproving the light efficiency of the LED chip. Besides, it can beobserved that electro-migration in these layers occurs less, thus theoverdrive performance of the LED chip can be improved. Furthermore, itis noted that the variation of the operating voltage of the LED chipwith time is decreased, according to the embodiments of the invention.Namely, the reliability of the LED chip can be maintained duringlong-term operation, according to the embodiments of the invention.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. On the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

What is claimed is:
 1. A light-emitting diode (LED) chip, comprising: anLED; and an electrode layer disposed on the LED, wherein the electrodelayer comprises a reflective metal layer and an adhesive layer betweenthe LED and the reflective metal layer, and wherein the reflective metallayer comprises: a first composition comprising Al or Ag; and a secondcomposition comprising Cu, Si, Sn, Pt, Au or a combination thereof,wherein a weight percentage of the second composition is greater than 0%and less than 20%.
 2. The chip as claimed in claim 1, wherein theelectrode layer further comprises a diffusion barrier layer disposed onthe reflective metal layer.
 3. The chip as claimed in claim 2, whereinthe electrode layer further comprises a bonding layer disposed on thediffusion barrier layer.
 4. The chip as claimed in claim 1, wherein thesecond composition further comprises Pd.
 5. A light-emitting diode (LED)chip, comprising: an LED; and a reflective metal layer disposed on theLED, wherein the reflective metal layer comprises: a first compositioncomprising Al or Ag; and a second composition comprising Cu, Si, Sn, Pt,Au or a combination thereof, wherein a weight percentage of the secondcomposition is greater than 0% and less than 20%.
 6. The chip as claimedin claim 5, further comprising a diffusion barrier layer disposed on thereflective metal layer.
 7. The chip as claimed in claim 6, wherein thesecond composition further comprises Pd.
 8. The chip as claimed in claim7, wherein the diffusion barrier layer comprises the first compositionand the second composition, wherein a weight percentage of the secondcomposition is greater than 0% and less than 20%.
 9. The chip as claimedin claim 7, further comprising a conductive metal layer disposed on thediffusion barrier layer.
 10. The chip as claimed in claim 9, wherein theconductive metal layer comprises the first composition and the secondcomposition, wherein a weight percentage of the second composition isgreater than 0% and less than 20%.
 11. The chip as claimed in claim 9,wherein the LED comprises: first and second conductivity-typesemiconductor layers; and an active layer disposed between the firstconductivity-type semiconductor layer and the second conductivity-typesemiconductor layer, wherein the second conductivity-type semiconductorlayer is disposed between the reflective metal layer and the activelayer, and wherein a portion of the conductive metal layer extendsthrough the diffusion barrier layer, the reflective metal layer, and aportion of the LED, so as to be in contact with the firstconductivity-type semiconductor layer.
 12. The chip as claimed in claim11, wherein the conductive metal layer comprises an opening, and thechip further comprises: an isolation layer disposed on the conductivemetal layer and filling the opening; and first and second bonding layersindividually disposed on the isolation layer, wherein a portion of thefirst bonding layer is in the opening and passes through the isolationlayer to be in contact with the diffusion barrier layer, and a portionof the second bonding layer extends through the isolation layer to be incontact with the conductive metal layer.
 13. The chip as claimed inclaim 12, wherein at least one of the first and second bonding layerscomprises the first composition and the second composition, and whereina weight percentage of the second composition is greater than 0% andless than 20%.
 14. The chip as claimed in claim 12, wherein theconductive metal layer comprises an opening, and the chip furthercomprises: a second conductive metal layer in the opening to be incontact with the diffusion barrier layer; an isolation layer disposed onthe conductive layer and filling the opening to cover a portion of thesecond conductive metal layer; and first and second bonding layersindividually disposed on the isolation layer, wherein a portion of thefirst bonding layer passes through the isolation layer to be in contactwith the second conductive metal layer, and a portion of the secondbonding layer extends through the isolation layer to be in contact withthe conductive metal layer.
 15. The chip as claimed in claim 14, whereinat least one of the first and second bonding layers comprises the firstcomposition and the second composition, and wherein a weight percentageof the second composition is greater than 0% and less than 20%.